STRANGE ENGINE NUMBER TO DATE

[sibur]

Hi all, I'm new to the forum and purchased my first Lister engine a couple of days ago. It's a runner and we're over the moon with it.
All it requires is a rub down repaint and the shiny bits polished.

I have been on a few sites today to try and date it, but am having trouble.  The number is -   234 8 DH 10 and the engine is a 1.5hp D. On the sites I looked at the engine looks like it's meant to have a five digit number, can anybody help please?
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